One of conventional electric power conversion devices is a DC/DC electric power conversion device that includes: two or more switching units each composed of two semiconductor switching elements, with the semiconductor switching elements in each switching unit being connected in series; an energy transfer capacitor for charging and discharging; and an inductor. The DC/DC electric power conversion device adjusts a ratio between input and output voltages, and the power direction, through operation in four kinds of switching modes (for example, see Patent Document 1).